Fully silicided linerless middle-of-line (mol) contact

ABSTRACT

A method of making a semiconductor device includes forming a source/drain region on a substrate; disposing a gate stack on the substrate and adjacent to the source/drain region, the gate stack including a gate spacer along a sidewall of the gate stack; disposing an inter-level dielectric (ILD) layer on the source/drain region and the gate stack; removing a portion of the ILD layer on the source/drain region to form a source/drain contact pattern; filling the source/drain contact pattern with a layer of silicon material, the layer of silicon material being in contact with the source/drain region and in contact with the gate spacer; depositing a metallic layer over the first layer of silicon material; and performing a silicidation process to form a source/drain contact including a silicide.

PRIORITY

This application is a continuation of and claims priority from U.S.patent application Ser. No. 14/967,736, filed on Dec. 14, 2015, entitled“A FULLY SILICIDED LINERLESS MIDDLE-OF-LINE (MOL) CONTACT,” which is acontinuation of and claims priority from U.S. patent application Ser.No. 14/856,918, filed on Sep. 17, 2015, entitled “A FULLY SILICIDEDLINERLESS MIDDLE-OF-LINE (MOL) CONTACT,” each application isincorporated herein by reference in its entirety.

BACKGROUND

The present invention relates to metal-oxide-semiconductor field-effecttransistors (MOSFET), and more specifically, to contacts in MOSFETtransistors.

The MOSFET is a transistor used for amplifying or switching electronicsignals. The MOSFET has a source, a drain, and a metal oxide gateelectrode. The metal gate is electrically insulated from the mainsemiconductor n-channel or p-channel by a thin layer of insulatingmaterial, for example, silicon dioxide or glass, which makes the inputresistance of the MOSFET relatively high. The gate voltage controlswhether the path from drain to source is an open circuit (“off”) or aresistive path (“on”).

The FinFET is a type of MOSFET. The FinFET is a double-gate ormultiple-gate MOSFET device that mitigates the effects of short channelsand reduces drain-induced barrier lowering. The “fin” refers to thenarrow channel between source and drain regions. A thin dielectric layeron either side of the fin separates the fin channel from the gate.

SUMMARY

According to an embodiment, a method of making a semiconductor deviceincludes forming a source/drain region on a substrate; disposing a gatestack on the substrate and adjacent to the source/drain region, the gatestack including a gate spacer along a sidewall of the gate stack;disposing an inter-level dielectric (ILD) layer on the source/drainregion and the gate stack; removing a portion of the ILD layer on thesource/drain region to form a source/drain contact pattern; filling thesource/drain contact pattern with a layer of silicon material, the layerof silicon material being in contact with the source/drain region and incontact with the gate spacer; depositing a metallic layer over the firstlayer of silicon material; and performing a silicidation process to forma source/drain contact including a silicide.

According to another embodiment, a method of making a semiconductordevice includes forming a source/drain region over a substrate;disposing a gate stack over the substrate and adjacent to thesource/drain region, the gate stack including a gate spacer along asidewall of the gate stack; disposing an ILD layer over the source/drainregion and the gate stack; removing a portion of the ILD layer over thesource/drain region to form a source/drain contact pattern; anddepositing a metal-silicon alloy into source/drain contact pattern tofill the source/drain contact pattern; and performing a silicidationprocess to form a silicide in the source/drain contact pattern, thesilicide being in contact with the source/drain region and in contactwith the gate spacer.

Yet, according to another embodiment, a semiconductor device includes asubstrate; a gate disposed over the substrate; a spacer arranged along asidewall of the gate; a source/drain disposed over the substrate andadjacent to the spacer; and a source/drain contact formed over and incontact with the source/drain and over and in contact with the spacer,the source/drain contact including a silicide disposed along a sidewallof the source/drain contact, over the spacer, and filled within thesource/drain contact.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The forgoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIGS. 1-9 illustrate exemplary methods of making semiconductor devicesaccording to a first embodiment, in which:

FIG. 1 is a cross-sectional side view of source/drain regions betweengate stacks disposed over a substrate;

FIG. 2 is a cross-sectional side view after etching to form source/draincontact via patterns over the source/drain regions;

FIG. 3 is a cross-sectional side view after etching the inter-leveldielectric (ILD) layer to widen the source/drain contact via opening;

FIG. 4 is a cross-sectional side view after filling the source/draincontact trenches with silicon;

FIG. 5 is a cross-sectional side view after recessing the silicon belowthe ILD layer;

FIG. 6 is a cross-sectional side view after depositing a conformal layerof a metal over the silicon and the ILD layer;

FIG. 7 is a cross-sectional side view after performing a silicidationprocess to form a silicide within the source/drain contact vias;

FIG. 8 is a cross-sectional side view after selectively removing theconformal metal layer;

FIG. 9 is a cross-sectional side view after forming the finalsource/drain contacts;

FIGS. 10-12 illustrate exemplary methods of making semiconductor devicesaccording to a second embodiment, in which:

FIG. 10 is a cross-sectional side view after depositing alternatingmetal layers and silicon layers in the source/drain contact via patternsof FIG. 3;

FIG. 11 is a cross-sectional side view after performing a silicidationprocess to form a silicide within the source/drain contact vias;

FIG. 12 is a cross-sectional side view after forming the finalsource/drain contacts; and

FIG. 13 illustrates an exemplary method of making a semiconductor deviceaccording to a third embodiment, in which a metal-silicon alloy isdeposited directly into the source/drain contact vias of FIG. 3, and asilicidation process is employed for form the silicide.

DETAILED DESCRIPTION

As semiconductor devices scale to smaller dimensions, contact resistancemay increase, which may decrease external device performance. Somemethods for decreasing contact resistance include changes to contactmaterials. Because metal liners used in contacts may have higherresistivity than bulk metals, increasing the proportion of metal linersto bulk metals in device contact vias may increase overall deviceresistance. Devices that include small, i.e., 10×10 nanometer (nm)square vias, for example, are the most negatively impacted by the highresistance liners.

Accordingly, various embodiments described herein provide devices andmethods of making semiconductor devices with source/drain contactswithout a metal liner. The methods form a low resistance via/contact tothe source/drain region of a transistor. In some embodiments, thesource/drain regions and vias are filled with, for example, amorphoussilicon, a metal, or a silicon-metal alloy. A low temperaturesilicidation is performed to provide a low resistance via/contactwithout a liner on the via sidewall. A barrier layer disposed onto thecontact prevents further silicidation. Like reference numerals refer tolike elements across different embodiments.

The following definitions and abbreviations are to be used for theinterpretation of the claims and the specification. As used herein, theterms “comprises,” “comprising,” “includes,” “including,” “has,”“having,” “contains” or “containing,” or any other variation thereof,are intended to cover a non-exclusive inclusion. For example, acomposition, a mixture, process, method, article, or apparatus thatcomprises a list of elements is not necessarily limited to only thoseelements but can include other elements not expressly listed or inherentto such composition, mixture, process, method, article, or apparatus.

As used herein, the articles “a” and “an” preceding an element orcomponent are intended to be nonrestrictive regarding the number ofinstances (i.e. occurrences) of the element or component. Therefore, “a”or “an” should be read to include one or at least one, and the singularword form of the element or component also includes the plural unlessthe number is obviously meant to be singular.

As used herein, the terms “invention” or “present invention” arenon-limiting terms and not intended to refer to any single aspect of theparticular invention but encompass all possible aspects as described inthe specification and the claims.

As used herein, the term “about” modifying the quantity of aningredient, component, or reactant of the invention employed refers tovariation in the numerical quantity that can occur, for example, throughtypical measuring and liquid handling procedures used for makingconcentrates or solutions. Furthermore, variation can occur frominadvertent error in measuring procedures, differences in themanufacture, source, or purity of the ingredients employed to make thecompositions or carry out the methods, and the like. In one aspect, theterm “about” means within 10% of the reported numerical value. Inanother aspect, the term “about” means within 5% of the reportednumerical value. Yet, in another aspect, the term “about” means within10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% of the reported numerical value.

Turning now to the Figures, FIGS. 1-9 illustrate exemplary methods ofmaking semiconductor devices according to a first embodiment. FIG. 1 isa cross-sectional side view of source/drain regions 120 (activeareas/regions) between gates 101 formed over a substrate (not shown).

Non-limiting examples of suitable substrate materials include Si(silicon), strained Si, SiC (silicon carbide), Ge (germanium), SiGe(silicon germanium), SiGeC (silicon-germanium-carbon), Si alloys, Gealloys, GaAs (gallium arsenide), InAs (indium arsenide), InP (indiumphosphide), or any combination thereof. Other examples of suitablesubstrates include silicon-on-insulator (SOI) substrates with buriedoxide (BOX) layers.

In one embodiment, the transistor is a FinFET device. The substrate isetched to pattern a fin in the substrate material.

The gates 101 include a gate stack and are formed over the substrate.When the device is a FinFET device, the gates 101 are formed over a fin.The gate stack includes high-k metal gates formed, for example, byfilling a dummy gate opening with one or more high-k dielectricmaterials, one or more workfunction metals, and one or more metal gateconductor materials. The high-k dielectric material(s) can be adielectric material having a dielectric constant greater than 4.0, 7.0,or 10.0. Non-limiting examples of suitable materials for the high-kdielectric material include oxides, nitrides, oxynitrides, silicates(e.g., metal silicates), aluminates, titanates, nitrides, or anycombination thereof. Examples of high-k materials include, but are notlimited to, metal oxides such as hafnium oxide, hafnium silicon oxide,hafnium silicon oxynitride, lanthanum oxide, lanthanum aluminum oxide,zirconium oxide, zirconium silicon oxide, zirconium silicon oxynitride,tantalum oxide, titanium oxide, barium strontium titanium oxide, bariumtitanium oxide, strontium titanium oxide, yttrium oxide, aluminum oxide,lead scandium tantalum oxide, and lead zinc niobate. The high-k materialmay further include dopants such as, for example, lanthanum andaluminum.

The high-k dielectric material layer may be formed by suitabledeposition processes, for example, chemical vapor deposition (CVD),plasma-enhanced chemical vapor deposition (PECVD), atomic layerdeposition (ALD), evaporation, physical vapor deposition (PVD), chemicalsolution deposition, or other like processes.

The work function metal(s) may be disposed over the high-k dielectricmaterial. The type of work function metal(s) depends on the type oftransistor. Non-limiting examples of suitable work function metalsinclude p-type work function metal materials and n-type work functionmetal materials. P-type work function materials include compositionssuch as ruthenium, palladium, platinum, cobalt, nickel, and conductivemetal oxides, or any combination thereof. N-type metal materials includecompositions such as hafnium, zirconium, titanium, tantalum, aluminum,metal carbides (e.g., hafnium carbide, zirconium carbide, titaniumcarbide, and aluminum carbide), aluminides, or any combination thereof.

A conductive metal is deposited over the high-k dielectric material(s)and workfunction layer(s) to form the gate stacks. Non-limiting examplesof suitable conductive metals include aluminum (Al), platinum (Pt), gold(Au), tungsten (W), titanium (Ti), or any combination thereof. Theconductive metal may be deposited by a suitable deposition process, forexample, CVD, PECVD, PVD, plating, thermal or e-beam evaporation, andsputtering. A planarization process, for example, chemical mechanicalplanarization (CMP), is performed to polish the surface of theconductive gate metal to form the gates 101.

In some embodiments, the width 143 of the gates 101 is in a range fromabout 10 nm to about 30 nm. In other embodiments, the width 132 of thegates 101 is in a range from about 12 to about 24 nm. Yet, in otherembodiments, the width 132 of the gates 101 is in a range about or inany range from about 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, and24 nm.

In some embodiments, the height 130 of the gates 101 is in a range fromabout 30 nm to about 100 nm. In other embodiments, the height 130 of thegates 101 is in a range from about 30 to about 40 nm. Yet, in otherembodiments, the height 130 of the gates 101 is about or in any rangefrom about 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, and 40 nm.

The gates 101 include a gate spacer 103 along a sidewall and in contactwith the source/drain regions 120. To form the gate spacers 103, aninsulating liner material is deposited over the gates 101 and etched byan anisotropic etching process, for example, reactive ion etching (ME).Non-limiting examples of suitable materials for the spacers 103 includedielectric oxides (e.g., silicon oxide), dielectric nitrides (e.g.,silicon nitride), dielectric oxynitrides, SiOCN, SiBCN, or anycombination thereof.

In some embodiments, the thickness 142 of the spacers 103 is in a rangefrom about 4 to about 10 nm. In other embodiments, the thickness 142 ofthe spacers 103 is in a range from about 2 to about 10 nm. Yet, in otherembodiments, the thickness 142 of the spacers 103 is about or in anyrange from about 2, 3, 4, 5, 6, 7, 8, 9, and 10 nm.

An insulating hard mask 102 (capping layer) is disposed over the gates101. Non-limiting examples of suitable materials for the hard mask 102include silicon nitride (SiN), SiOCN, SiBCN, or a combination thereof.

In some embodiments, the thickness 131 of the hard mask 102 is in arange from about 20 to about 50 nm. In other embodiments, the thickness132 of the hard mask 102 is in a range from about 20 to about 30 nm.Yet, in other embodiments, the thickness 132 of the hard mask 102 isabout or in any range from about 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,and 30 nm.

The source/drain regions 120 are formed between the gates 101 and overthe substrate. In some embodiments, the source/drain regions 120 areformed by growing an epitaxial growth layer over the substrate materialbeneath the gates 101. In other embodiments, the source/drain regions120 may be formed by incorporating dopants into the substrate.

An epitaxial growth process may be performed to deposit a crystallinelayer onto a crystalline substrate beneath. The underlying substrateacts as a seed crystal. Epitaxial layers may be grown from gaseous orliquid precursors. Epitaxial growth layers may be grown usingvapor-phase epitaxy (VPE), molecular-beam epitaxy (MBE), liquid-phaseepitaxy (LPE), or other suitable process. The epitaxial growth mayinclude, for example, silicon, silicon germanium, and/or carbon dopedsilicon (Si:C) silicon. The epitaxial growth can be doped duringdeposition by adding a dopant or impurity to form a silicide. Thesilicon may be doped with an n-type dopant (e.g., phosphorus or arsenic)or a p-type dopant (e.g., boron or gallium), depending on the type oftransistor.

In some embodiments, the thickness 121 of the epitaxial growth formingthe source/drain regions 120 is in a range from about 10 to about 50 nm.In other embodiments, the thickness 121 of the epitaxial growth formingthe source/drain regions 120 is in a range from about 10 to about 20 nm.Yet, in other embodiments, the thickness 121 of the epitaxial growthforming the source/drain regions 120 is about or in any range from about10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 nm.

In some embodiments, the width 141 of the epitaxial growth forming thesource/drain regions 120 is in a range from about 10 to about 50 nm. Inother embodiments, the width 141 of the epitaxial growth forming thesource/drain regions 120 is in a range from about 10 to about 18 nm.Yet, in other embodiments, the width 141 of the epitaxial growth formingthe source/drain regions 120 is about or in any range from about 10, 11,12, 13, 14, 15, 16, 17, and 18 nm.

In one embodiment, the total width 140 of the epitaxial growth formingthe source/drain 120, gate 101, and gate spacers 103 is in a range fromabout 3 to about 10 nm. In another embodiment, the total width 140 ofthe epitaxial growth forming the source/drain 120, gate 101, and gatespacers 103 is in a range from about 34 to about 54 nm. Yet, in otherembodiments, the total width 140 of the epitaxial growth forming thesource/drain 120, gate 101, and gate spacers 103 is about or in anyrange from about 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, and 44 nm.

An inter-level dielectric (ILD) layer 110 is deposited as a blanketlayer over the gates 101 and the source/drain regions 120. The ILD layer110 may be formed from, for example, a low-k dielectric oxide, includingbut not limited to, silicon dioxide, spin-on-glass, a flowable oxide, ahigh density plasma oxide, borophosphosilicate glass (BPSG), or anycombination thereof. The ILD layer 110 deposited by a suitabledeposition process, including, but not limited to CVD, PVD, plasmaenhanced CVD, atomic layer deposition (ALD), evaporation, chemicalsolution deposition, or like processes.

In some embodiments, the thickness 132 of the ILD layer 110 over thehard masks 102 over the gates 101 is in a range from about 30 to about100 nm. In other embodiments, the thickness 132 of the ILD layer 110 isin a range from about 15 to about 25 nm. Yet, in other embodiments, thethickness 132 of the ILD layer 110 is about or in any range from about15, 16, 17, 18, 19, 20, 21, 22, 23, 24, and 25 nm.

FIG. 2 is a cross-sectional side view after etching to form source/draincontact via patterns 201 over the source/drain regions 120. An etchingprocess is employed to remove a portion of the ILD layer 110 over thesource/drain regions 120 between the gates 101. The ILD layer 110 isremoved down to the level of the source/drain regions 120. A portion ofthe ILD layer 110 over the spacers 103 is also removed.

The ILD layer 110 may be etched by, for example, a chemical mechanicalplanarization (CMP) process or a reactive ion etching (ME) process.

In one embodiment, the source/drain contact via pattern 201 has a depth213 in a range from about 50 to about 100 nm. In other embodiments, thesource/drain contact via pattern 201 has a depth 213 in a range fromabout 60 to about 70 nm. Yet, in other embodiments, the source/draincontact via pattern 201 has a depth 213 in a range about or in any rangefrom about 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, and 70 nm.

In some embodiments, the source/drain contact via pattern 201 has awidth 211 in a range from about 15 to about 30 nm. In other embodiments,the source/drain contact via pattern 201 has a width 211 in a range fromabout 20 to about 28 nm. Yet, in other embodiments, the source/draincontact via pattern 201 has a width 211 in a range about or in any rangefrom about 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, and 30 nm.

The spacers 103 and/or a portion of the hard mask 102 are recessed byemploying an etching process. The spacers 103 are etched below the levelof the ILD layer 110 and the hard mask layer 102. The etching processmay be, for example, a selective RIE process.

The spacers 103 are recessed by an amount in a range from about 10 toabout 20 nm. In some embodiments, the spacers 103 are recessed by anamount in a range from about 5 to about 15 nm. Yet, in otherembodiments, the spacers 103 are recessed by an amount about or in anyrange from about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15 nm.

After recessing the spacers 103, the width 212 of the ILD layer 110remaining between source/drain contact via patterns 201 is in a rangefrom about 15 to about 30 nm. In some embodiments, the width 212 of theILD layer 110 remaining between source/drain contact via patterns 201 isin a range from about 15 to about 25 nm. Yet, in other embodiments, thewidth 212 of the ILD layer 110 remaining between source/drain contactvia patterns 201 is about or in any range from about 15, 16, 17, 18, 19,20, 21, 22, 23, 24, and 25 nm.

FIG. 3 is a cross-sectional side view after etching the ILD layer 110 towiden the source/drain contact via 201 openings 310. The ILD layer 110is etched (or pre-cleaned) by, for example, using an acidic or aqueoussolution to flush the surface of the ILD layer 110. The pre-cleanprocess may remove oxides from the surface of the ILD layer. Thepre-clean process may include employing, for example, a dilutehydrofluoric acid process.

In some embodiments, the width 211 of the source/drain contact viapattern 201 openings 310 increases by an amount in a range from about 5to about 10 nm. In other embodiments, the width 211 of the source/draincontact via pattern 201 openings 310 increases by an amount in a rangefrom about 5 to about 10 nm. Yet, in other embodiments, the width 211 ofthe source/drain contact via pattern 201 openings 310 increase by anamount about or in any range from about 5, 6, 7, 8, 9, 10, 11, 12, 13,14, and 15 nm.

As material is removed from the ILD layer 110 to widen the openings 310,the thickness 132 of the ILD layer 110 also decreases. The thickness 132of the ILD layer 110 decreases by an amount in a range from about 20 toabout 40 nm. In some embodiments, the thickness 132 of the ILD layer 110decreases by an amount in a range from about 1 to about 10 nm.

FIG. 4 is a cross-sectional side view after filling the source/draincontact via patterns 201 with silicon 401, for example, amorphoussilicon (aSi) or polycrystalline silicon (polysilicon). The aSi orpolysilicon may be deposited using a blanket deposition process.Non-limiting examples of suitable deposition processes include CVDprocesses.

The aSi or polysilicon also may be deposited using an epitaxial growthprocess, as described above. The epitaxial growth process may beselective or non-selective.

FIG. 5 is a cross-sectional side view after recessing the silicon 401 toa level below the ILD layer 110. The silicon 401 is recessed to a levelthat is below the hard mask 102 and above the recessed spacers 103.

An etching process, for example, a RIE process may be employed to recessthe silicon (remove a portion of the silicon 401 material).

FIG. 6 is a cross-sectional side view after depositing a conformalmetallic layer 601 over the recessed silicon 401 and the ILD layer 110.The conformal metallic layer 601 may be deposited using a depositionprocess, which depends on the type of refractory metal(s). Thedeposition process may include, but is not limited to, chemical vapordeposition CVD, PVD, ALD, or any combination thereof.

Non-limiting examples of metals for the conformal metallic layer 601include conductive metals and/or refractory metals. Non-limitingexamples of conductive metals include nickel, titanium, gold, silver,platinum, palladium, or a combination thereof. Non-limiting examples ofrefractory metals include niobium, molybdenum, tantalum, tungsten,rhenium, titanium, vanadium, zirconium, hafnium, osmium, iridium, or acombination thereof.

FIG. 7 is a cross-sectional side view after performing a silicidationprocess to form a silicide 701 within the source/drain contact viapatterns 201. The silicidation process is a low temperature silicidationprocess. The silicidation process substantially fully consumes thesilicon 401 to form a metal silicide that includes the metal from themetallic layer 601 and the silicon 401. The silicidation processincludes thermal annealing to produce a metal-rich silicon material, ora metal silicide. In one exemplary embodiment, the silicide includesnickel silicide.

The thermal annealing is performed at a low temperature, for example, ata temperature in a range from about 300 to about 600° C. In someembodiments, the silicidation process is performed at a temperature in arange from about 300 to about 600° C.

FIG. 8 is a cross-sectional side view after selectively removing theunreacted metallic layer 601. The portion of the metallic layer 601 thatwas not consumed in the silicidation process to form the silicide 701 isremoved.

The unreacted metallic layer 601 may be selectively removed by employingan etching process. The etching process may be, for example, an RIEprocess.

FIG. 9 is a cross-sectional side view after forming the finalsource/drain contacts 901. The source/drain contacts 901 are formed by,for example, depositing a layer of conductive material and/or moresilicide material over the silicide 701. Once the layer of conductivematerial is deposited, a planarization process, such as RIE, isperformed to remove the excess conductive material disposed over the ILDlayer 110 and to form the source/drain contacts 901.

FIGS. 10-12 illustrate exemplary methods of making semiconductor devicesaccording to a second embodiment. FIG. 10 is a cross-sectional side viewafter depositing metallic layers 1001 between silicon layers 401 in thesource/drain contact vias of FIG. 3.

One or more metallic layers 1001 may be deposited between the silicon401 (aSi or polysilicon). The metallic layers 1001 are deposited overthe silicon layers 401. The metallic layer(s) 1001 include any of theabove described conductive and refractory metals described for metalliclayer 601 (see FIG. 6). The alternating layers of metallic layer 1001and silicon layer 401 may be formed by alternate deposition and etchingprocesses. Including the additional metallic layers 1001 between thesilicon layers 401, instead of a bulk silicon layer as shown in FIGS. 5and 6, may reduce the anneal time for silicidation (see FIG. 11 below).

In one embodiment, the source/drain contact via patterns 201 are filledby depositing a first amorphous silicon layer onto the source/drainregion, depositing a metallic layer onto the first amorphous siliconlayer, depositing a second amorphous silicon layer onto metallic layer,and performing a silicidation process to form the silicide. Additionalmetallic layers and/or amorphous silicon layers may be included.

In one exemplary embodiment, the metallic layer 1001 includes Ni, andthe silicon layer 401 includes aSi. Additional contact layer(s) may beinserted between the source/drain regions 120 and the silicon layers401.

FIG. 11 is a cross-sectional side view after performing a silicidationprocess to form a silicide 1101 within the source/drain contact vias.The silicidation process is a low temperature silicidation process andis described above in FIG. 7. The silicidation process substantiallyfully consumes the silicon 401 to form a metal silicide, including themetal from the metallic layer 1001 and the silicon 401.

FIG. 12 is a cross-sectional side view after forming the finalsource/drain contacts 1201. The source/drain contacts 1201 are formedby, for example, depositing a layer of conductive material and/or moresilicide material over the silicide 1101. Once the layer of conductivematerial is deposited, a planarization process, such as an RIE process,is performed to remove the excess conductive material disposed over theILD layer 110 and to form the source/drain contacts 901.

FIG. 13 illustrates an exemplary method of making a semiconductor deviceaccording to a third embodiment. A metal-silicon alloy is depositeddirectly into the source/drain contact vias 201 of FIG. 3. Themetal-silicon alloy may be deposited using a deposition process, forexample, a PVD process (e.g., sputtering) or a CVD process. Themetal-silicon includes a refractory or conductive metal described abovefor conformal metallic layer 601.

A silicidation process is performed to convert the metal-silicon alloyinto the silicide 1301. The silicidation process may be a lowtemperature silicidation process described above in FIG. 7.

The metal-silicon alloy will be deposited as a blanket layer onto theILD layer 110, as well as into the source/drain contact vias 201. Aplanarization process, for example, a process including a CMP process,is employed to polish the surface of the ILD layer 110 and form thefinal source/drain contacts 1302.

The final source/drain contacts 901, 1201, 1302 are formed without usinga high resistance contact liner and consist essentially of the silicidematerial. The final source/drain contacts 901, 1201, 1302 areborderless. The source/drain contacts 901, 1201, 1301 include a firstportion adjacent to the spacer and a second portion over the spacer, thefirst portion having a width that is less than the second portion.

Employing the low temperature silicidation process provides a lowresistance source/drain contact (via) without a liner along any of thecontact sidewalls. The final source/drain contacts 901, 1201, 1302 havelow contact resistance, e.g., about 10 ohm to about 30 ohm.

As described above, various embodiments described herein provide devicesand methods of making semiconductor devices with source/drain contactswithout a metal liner. The methods form a low resistance via/contact tothe source/drain region of a transistor. The source/drain regions andvias are filled with an amorphous silicon (or polysilicon), a refractorymetal, or a silicon/refractory metal alloy. A low temperaturesilicidation is performed to provide a low resistance via/contactwithout a liner on the via sidewalls. A barrier layer disposed onto thecontact prevents further silicidation.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, element components,and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

The diagrams depicted herein are just one example. There may be manyvariations to this diagram or the steps (or operations) describedtherein without departing from the spirit of the invention. Forinstance, the steps may be performed in a differing order or steps maybe added, deleted or modified. All of these variations are considered apart of the claimed invention.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A method of making a semiconductor device, themethod comprising: forming a source/drain region on a substrate;disposing a gate stack on the substrate and adjacent to the source/drainregion, the gate stack comprising a gate spacer along a sidewall of thegate stack; disposing an inter-level dielectric (ILD) layer on thesource/drain region and the gate stack; removing a portion of the ILDlayer on the source/drain region to form a source/drain contact pattern;filling the source/drain contact pattern with a layer of siliconmaterial, the layer of silicon material being in contact with thesource/drain region and in contact with the gate spacer; depositing ametallic layer over the first layer of silicon material; and performinga silicidation process to form a source/drain contact comprising asilicide.
 2. The method of claim 1, wherein the silicidation processincludes a low temperature annealing process.
 3. The method of claim 2,wherein the low temperature annealing process substantially fullyconsumes the silicon material to form the metal silicide.
 4. The methodof claim 3, wherein the metal silicide is nickel silicide.
 5. The methodof claim 2, wherein the low temperature annealing process is performedat a temperature in a range from about 300 to about 600° C.
 6. Themethod of claim 1, wherein the first metallic layer comprises arefractory metal.
 7. The method of claim 1, wherein the source/draincontact consists essentially of the silicide.
 8. The method of claim 1,wherein filling the source/drain contact pattern with the silicidefurther comprises depositing another silicon layer onto the metalliclayer and depositing another a metallic layer onto the another siliconlayer.
 9. The method of claim 1, wherein performing the silicidationprocess comprises performing a thermal annealing process at atemperature in a range from about 300 to about 600° C.
 10. The method ofclaim 1, further comprising pre-cleaning the source/drain contactpattern after removing a portion of the ILD layer.
 11. A method ofmaking a semiconductor device, the method comprising: forming asource/drain region over a substrate; disposing a gate stack over thesubstrate and adjacent to the source/drain region, the gate stackcomprising a gate spacer along a sidewall of the gate stack; disposingan ILD layer over the source/drain region and the gate stack; removing aportion of the ILD layer over the source/drain region to form asource/drain contact pattern; depositing a metal-silicon alloy intosource/drain contact pattern to fill the source/drain contact pattern;and performing a silicidation process to form a silicide in thesource/drain contact pattern, the silicide being in contact with thesource/drain region and in contact with the gate spacer.
 12. The methodof claim 11, further comprising recessing the gate spacer after removinga portion of the ILD layer.
 13. The method of claim 11, whereindepositing the metal-silicon alloy comprises a physical vapor depositionprocess.
 14. The method of claim 13, wherein the physical vapordeposition is a sputtering process.
 15. The method of claim 11, whereinthe metal-silicon alloy comprises a nickel-silicon alloy.
 16. The methodof claim 1, wherein the silicidation process includes a low temperatureannealing process.
 17. The method of claim 16, wherein the lowtemperature annealing process substantially fully consumes the siliconmaterial to form the metal silicide.
 18. The method of claim 17, whereinthe metal silicide is nickel silicide.
 19. The method of claim 11,wherein the low temperature annealing process is performed at atemperature in a range from about 300 to about 600° C.
 20. The method ofclaim 11, further comprising pre-cleaning the source/drain contactpattern after removing a portion of the ILD layer.